1. Field of the Invention
The present invention relates to processes for the preparation of resorcinol, and more particularly to the preparation of resorcinol by hydroperoxidation of diisopropylbenzene.
2. Description of the Prior Art
Resorcinol, or 1,3-benzenediol, has numerous industrial applications, such as its use in the manufacture of fluorescein, eosin, and other dyes, synthetic drugs, and photographic developers or its use as a reagent, reducing agent, external dehydrant, antiseptic, antiferment and bactericide. A well known method of preparing resorcinol has been via a sulfonation-fusion process. Another known method is via the cyclization of methyl 4-oxocaproate from methyl acrylate and acetone followed by dehydrogenation.
In 1972, researchers at the Stanford Research Institute reviewed a new route for the preparation of resorcinol via hydroperoxidation. The Stanford process involves production of a m-diisopropylbenzene (m-DIPB) by alkylation of benzene and/or cumene with propylene, followed by oxidation of the m-DIPB to the diisopropylbenzene dihydroperoxide (DHP). The DHP is decomposed with the aid of an acid catalyst to form resorcinol and acetone.
Numerous patents have since issued which pertain to the preparation of resorcinol by hydroperoxidation.
One commercial process, believed to be practiced by the Sumitomo Chemical Company, Ltd. is described in part by Suda et al. U.S. Pat. No. 3,953,521, British Patent Specification No. 921,557, Suda et al. U.S. Pat. No. 3,950,431, Suda et al. U.S. Pat. No. 3,923,908, Suda et al. U.S. Pat. No. 3,928,469, and Japanese Pat. No. 61-327 and Japanese Kokai No. 58-88357. The Sumitomo process involves the continuous production of m- and p-DHP by hydroperoxidation of m- and p-DIPB in liquid phase using an alkali catalyst, such as 10-20 vol % of a 2% sodium hydroxide (NaOH) solution at 95.degree.-115.degree. C. and air at a pressure within the range of atmospheric to 10 atmospheres. The hydroperoxidation product is extracted with a 4% aqueous sodium hydroxide solution to separate DHP and m-diisopropylbenzene hydroxyhydroperoxide (HHP) from unreacted m-DIPB and diisopropylbenzene monohydroperoxide (MHP). The MHP/m-DIPB fraction is recycled to the hydroperoxidation reaction vessel. The DHP/HHP fraction, in the form of an aqueous solution containing sodium salts of DHP and HHP, is heated to 80.degree. C. and extracted with methyl isobutyl ketone (MIBK) to recover DHP and HHP. The MIBK solution of DHP/HHP is then washed with an organic solvent to reduce the HHP content, and mixed with an acid catalyst, such as 0.5-2% concentrated sulfuric acid (H.sub.2 SO.sub.4) and, in some instances, hydrogen peroxide (H.sub.2 O.sub.2) to decompose the DHP to either resorcinol or hydroquinone and acetone. The decomposition product is then neutralized with an aqueous ammonia solution, then distilled to obtain crude resorcinol or hydroquinone. Methods for purifying the crude resorcinol are described in Suda et al. U.S. Pat. Nos. 3,929,920; 3,911,030, and 3,969,420, and Japan Kokai No. 78-53626 and British Pat. No. 2,061,926 A.
Another commercial process, believed to be practiced by Mitsui Petrochemical Industries, is described in Nambu et al. U.S. Pat. No. 4,237,319, Imai et al. U.S. Pat. No. 4,267,387, Nakagawa et al. U.S. Pat. No. 4,283,570, Imai et al. U.S. Pat. No. 4,339,615, and Japan Kokai Nos. 61-180764 and 59-212440. The Mitsui process involves the hydroperoxidation of m-DIPB with molecular oxygen under aqueous alkaline conditions, for example, in the presence of 2% sodium hydroxide at 80.degree. C.-110.degree. C. for a period sufficient to react at least 90% of the DIPB. The hydroperoxidation product is dissolved in toluene and the aqueous sodium hydroxide solution is recycled to the hydroperoxidation reaction vessel for further use. The toluene solution is treated with excess hydrogen peroxide in the presence of small amounts of sulfuric acid to convert HHP and m-diisopropylbenzene dicarbinol (DCL) to DHP. The by-product water is azeotropically continuously removed. The toluene solution of DHP is then decomposed to resorcinol and acetone with concentrated sulfuric acid in substantial absence of hydrogen peroxide. The decomposition product is washed with aqueous sodium sulfate (Na.sub.2 SO.sub.4) and distilled to obtain crude resorcinol.
A process for recovery of the resorcinol from the acetone/resorcinol, mixture is described in Hashimoto et al. U.S. Pat. No. 4,273,623. The acid-decomposition reaction mixture is subjected to distillation to separate the resorcin containing concentrate from the acetone, wherein water is added to the decomposition reaction mixture in 20-70% by weight based on the weight of the resorcinol prior to distillation. Additional methods of purifying the crude resorcinol are described in Hashimoto et al. U.S. Pat. No. 4,239,921 and Canadian Pat. No. 1,115,733.
The commercial processes described above each include a peroxidation step employing oxygen or air and aqueous sodium hydroxide for converting DIPB to DHP and other by-products, an extraction step for separating DHP from the peroxidation by-products, an acid cleavage step employing sulfuric acid for decomposing DHP to either resorcinol or hydroquinone and acetone, a neutralization step and a distillation step to purify the crude resorcinol or hydroquinone.
The extraction step in the Sumitomo process includes a caustic extraction with 4% sodium hydroxide followed by organic extraction with MIBK. The Sumitomo process employs hydrogen peroxide in addition to the sulfuric acid in the acid cleavage step. The extraction step in the Mitsui process involves only organic extraction with toluene and is followed by oxidation with hydrogen peroxide and removal of water.
It is believed that neutralization in the Sumitomo process is by means of aqueous ammonia and removal of aqueous ammonium hydrogen sulfate ((NH.sub.4)HSO.sub.4). It is also believed that neutralization in the Mitsui process is by means of aqueous sodium sulfate and subsequent removal of aqueous sodium hydrogen sulfate (NaHSO.sub.4). The organic solvents in each process, MIBK and toluene, respectively, are removed in the distillation step and recycled for use in the organic extraction step.
The hydroperoxidation of DIPB produces a variety of by-products in addition to the desired DHP. Isolation of DHP from the oxidation products without causing its decomposition has been the object of several patent disclosures. British Patent Application GB NO. 2 071 662 A discloses the use of superacids such as boron trifluoride in the preparation of resorcinol from m-DIPB. British Pat. No. 921,557, referenced above, disclosed the principle that DHP can be extracted from aqueous alkaline solutions in a much more favorable manner at higher temperatures (e.g. 80.degree. C.) than ambient temperature. The direct extraction method, however, has a very serious problem; that is, the decomposition of DHP to HHP (and to a lesser degree to DCL) during the alkaline extraction process. Sumitomo Chemical Company, Ltd. owns several patents dealing with a method for extracting DHP. One Sumitomo process described in Canadian Pat. No. 1,056,407, discloses extracting DHP by a counter current multistage extraction with a temperature gradient between each stage and with all of the extractions being made at a temperature from 0.degree. to 85.degree. C. and the aqueous alkali solution being fed to the lower temperature zone. Another Sumitomo patent, U.S. Pat. No. 3,932,528, disclosed that in order to prevent the DHP loss during the alkaline extraction, 0.01 to 1 wt % of ammonia or aromatic amine (based on the weight of the solution) is added to the aqueous alkaline solution.
An object of the present invention is to improve the yield of resorcinol in a commercial process. A further object of the invention is to improve the selectivity to DHP in the hydroperoxidation step.